Chromatin regions, genes and pathways that confer susceptibility to chemical-induced DNA damage ABSTRACT Genetic variability has a major impact on susceptibility to common diseases, responses to drugs and toxicants, and influences disease-related outcomes. In addition, the links between genetic variability, toxicity outcomes and epigenetics are being actively explored. However, studies of Gene Environment Epigenetics are difficult as they involve interrogation of multiple individuals, exposure doses/times, tissue types, -omics endpoints and various toxicity phenotypes. This proposal aims to identify and validate chromatin regions, genes and pathways that confer susceptibility to environmental chemical-induced and metabolism-associated DNA damage. We will perform a series of proof-of-principle studies of the interplay between DNA damage induced by 1,3-butadiene, a genotoxic carcinogen, genetics, and epigenetics. We have extensive experience performing toxicology studies in the mouse (Collaborative Cross, CC) and human (1000 Genomes lymphoblast cell lines) population-based models. First, we will determine expression and chromatin quantitative trait loci (QTL) of butadiene genotoxicity in mouse tissues. We will test the hypothesis that strain- and tissue-specific variation in butadiene-induced DNA damage is controlled by the genetic variability-dependent background states in chromatin and gene expression. We will use tissues (liver, lung and kidney) from a study of 50 CC strains exposed to butadiene and will evaluate butadiene DNA damage and identify regions of active/repressed enhancers and promoters. Second, we will determine dose- and time-effects of butadiene-induced DNA damage in the context of background and treatment-induced chromatin and transcriptional states. We will test the hypothesis that butadiene exposure modifies strain- and tissue-specific epigenetic states in a dose-dependent manner and that DNA damage-associated effects on chromatin persist. We will examine inter- vs intra-strain variability, dose- and time-dependency in select CC strains. Third, we will characterize the extent of population variability in response to butadiene metabolites in a human in vitro population model. We will test the hypothesis that human lymphoblasts can be used to map susceptibility loci for butadiene genotoxicity. Fourth, we will validate the discoveries of the transcriptional and epigenetic mediators of strain-dependent DNA damage by butadiene in a human in vitro population-based model. We will test the hypothesis that genetic background- dependent transcriptional and epigenetic states confer susceptibility/resistance to butadiene-induced DNA damage. We will evaluate chromatin states and expression coupled with assays for DNA adducts. Overall, this work will demonstrate the interplay among environment (i.e., chemical exposure), genetics, and epigenetics by studying effects of 1,3-butadiene, an industrial toxicant and model genotoxic carcinogen. Human relevance and feasibility are justified by the focus on a fundamental mechanism of toxicity and carcinogenesis, the fact that butadiene is a known human and rodent carcinogen, and our previous work demonstrating butadiene effects of chromatin, histone modifications and other epigenetic states in a strain- and tissue-dependent manner.
Inter-individual differences in toxicity of chemicals and drugs are determined by complex interactions between our inherited DNA variants and other factors. This study will use an example of butadiene, a toxic chemical that in present in cigarette smoke and to which people can also be exposed at work if they work with rubber, to study how our DNA sequence may determine who may be more susceptible to butadiene-induced damage to our cells. We will use mice and human cells that represent genetic diversity in a population and use new molecular assays to find linkages between the chemical, our genes and disease.
